Some medicinally active pharmaceutical compositions can be administered directly to humans and animals without the need for an excipient. For instance, aspirin can be pressed into a tablet which has sufficient mechanical integrity to remain intact during packaging, shipping and storage prior to ingestion. However, most biologically active compounds require an excipient for effective administration. For instance, many biologically active compounds require a binder, disintegrant, lubricant, coating agent, emulsifying agent or filler to be commercially viable as a pharmaceutical product.
Today, some chemical compounds that offer promising results as pharmacological agents are complex structures that are difficult to solubilize by any emulsifying/dispersing agents that are acceptable for utilization as excipients. The inability to disperse such compounds in a conventional excipient can destroy the viability of the compound for utilization as a pharmaceutical product. This is, of course, because it is critical to disperse such compounds in an agent that will allow proper and effective bioavailability.
Excipients are frequently required for stabilizing blends of liquid biologically active compounds that are not mutually soluble. Excipients which are capable of suspending and/or dispersing the biologically active compound are also commonly used to improve the bioavailability of lipid soluble compounds. In many cases, excipients that are capable of solubilizing a biologically active compound can be used to improve the efficacy of the biological agent by virtue of more efficient delivery.
The dispersibility of biologically active compounds that are difficult to solubilize can often be improved by reducing the particle size of the chemical agent. The dispersibility of such agents can also sometimes be improved by utilizing an optimal emulsifying/dispersing excipient. The solubility of some biologically active agents such as celecoxib (the cyclooxygenase-2 inhibitor found in Celebrex) can also be improved by controlling the crystal structure of the active ingredient. However, in many cases, even though a stable dispersion may form, the bioavailability of the active ingredient may still be limited. For instance, an insoluble but dispersed biologically active agent might be ingested and passed completely through the gastrointestinal tract of the subject being treated without any of the active ingredient being absorbed by the subject. Accordingly, the biologically active agent would be totally ineffective even though it might be in the form of a stable liquid dispersion.